1. Field of the Invention
The invention relates to an illumination device and an image display apparatus, and more particularly, to an illumination device used as a light source of a projection type image display apparatus such as a projector, and an image display apparatus including the illumination device.
2. Description of the Related Art
In recent years, in regard to watching movies at home, a presentation at a meeting, or the like, the opportunities to use a projection-type image display apparatus, such as a projector, have been increasing. In such a projector, as a light source, for example, a discharge type lamp, such as mercury lamp, having a high brightness is generally used. In addition, with the recent progress in the development techniques for solid-state light emitting devices (for example, semiconductor lasers, light emitting diodes, or the like), there has been also suggested a projector using the solid-state light emitting device (for example, see JP-A-2010-86815).
The projector disclosed in JP-A-2010-86815 is a DLP (Digital Light Processing: registered trademark) type projector. In such a type of projector, images are displayed in full color through a time division display of approximately several thousand times per second for the different colors. Therefore, in the projector of JP-A-2010-86815, a red color light-emitting device, a green color light emitting device, and a blue color light emitting device those utilizing the solid-state light emitting device are separately prepared, and emitted light from each light-emitting device is time-divisionally controlled, and is emitted to the outside to display image light.
In addition, each of the light emitting devices, which are used in the projector of JP-A-2010-86815, includes a light emitting wheel that is rotatably driven, a light emitting material that is formed on a surface of the light emitting wheel and absorbs excitation light and emits light of a predetermined color, and an excitation light source (solid-state light emitting device) that emits excitation light. In addition, as the excitation light source used in each of the light emitting devices, a light source that emits excitation light with a wavelength band shorter than that of light emitted from the light emitting material is used.